We propose a post-doctoral training program in pediatric infectious diseases and immunity (PIDI-TP) based in the Pediatric Infectious Diseases Division of Washington University (WU)/St. Louis Children's Hospital. The long-term objective is to train academic physician-scientists to carry out research in pediatric infectious diseases including host response to infections. WU Medical Center offers an outstanding training environment for physician-scientists with nationally recognized hospitals conjoined with one of the nation's premier biomedical research facilities. Many Washington University faculty members are leading investigators in infectious diseases and human immunology. PIDI-TP will also take advantage of the WU Genome Institute, one of the world's most advanced genome sequencing centers that has played a leading role in the Human Microbiome Project. PIDI-TP mentors, drawn from the WU Departments of Pediatrics, Medicine, Pathology & Immunology, and Molecular Microbiology are highly successful investigators with independent research programs and experience in mentoring physician-scientists. The PIDI-TP Program Director will be Gregory Storch, Professor of Pediatrics and Director of the Division of Pediatric Infectious Diseases. The co-Program Director will be Thad Stappenbeck, Associate Professor of Pathology & Immunology. An Advisory Committee consisting of three senior WU faculty members and one distinguished outside member will advise the PD and co-PD. An Executive Committee will oversee recruitment and selection of trainees, monitor the performance and career development of trainees, and evaluate program operations and outcomes. Trainees will also report to Scholarship Oversight Committees, whose findings will be reviewed by the PD, co-PD, and Executive Committee. Support is requested for two trainees per year, to be recruited from pediatric fellowship programs in Infectious Diseases, Rheumatology, Neonatology, Allergy/Pulmonary/Immunology, Nephrology, and Critical Care, and from residents at St. Louis Children's Hospital, especially those with MD and PhD degrees. This pool of applicants is sufficient to fill the positions requested. Trainees will be assigned to one of three tracks: Pathogens, Host, and Genomics/Microbiome/Pathogen Discovery. Each PIDI-TP trainee will have a major research experience under the supervision of a program mentor. A Core Curriculum will provide training in study design, biostatistics, research ethics, human subjects, animal subjects, scientific writing, preparation of grants, and genomics, and will be supplemented by an individualized curriculum, specific for the trainee's chosen track. Trainees will also receive assistance in career planning and in preparation for subspecialty Board examinations. Career development will be monitored by research mentors, the PD and co-PD, the Executive Committee and the SOCs. Program evaluation will include short-term and long-term metrics plus input from current and past trainees. Efforts will be made to enhance diversity of trainees and mentors.